Opportunistic Sightings of Dolphins (MAMMALIA, CETACEA, DELPHINIDAE) in the North Coast of Bahia State, Northeastern Brazil, Between 2001 and 2006

Abstract

Using opportunistic platforms to study humpback whales (Megaptera novaeangliae) during their breeding season, from July to November, we analyzed the distribution of dolphin sightings in a poorly studied area, the north coast of Bahia State, Brazil. Between 2001 and 2006, more than 500 days of surveys were performed (2360 h of effort), in which 93 groups of dolphins were sighted from Itacare (14° 53′S, 38° 15′W) to Subauma (12° 30′S; 37° 63′W): 58 (62.4%) bottlenose dolphin, Tursiops truncatus; 21 (22.6%) estuarine dolphin, Sotalia guianensis; 7 (7.5%) -toothed dolphin, Steno bredanensis; 3 (3.2%) Clymene’s Dolphin, Stenella clymene; 2 (2.1%) pygmy killer whale, Feresa attenuata; 1 (1.1%) melon-headed dolphin, Peponocephala electra and 1 (1.1%) Atlantic Spotted dolphin, Stenella frontalis. Group size and depth range were: 1–30 for T. truncatus (10–150 m); 1–35 for S. guianensis (4–60 m); 1–6 for S. bredanensis (27–45 m); 1–100 for S. clymene (42–121 m); 5–6 for F. attenuata (97–200 m); 2 for S. frontalis at 51 m and 20 for P. electra at 150 m. The more frequent sightings of Tursiops truncatus and Sotalia guianensis are probably related to their known distribution patterns in Brazilian coastal waters. The sightings reported to S. guianensis add new information in a previously unstudied area. The records of pelagic species such as Stenella clymene, Feresa attenuata and Peponocephala electra, can be related to the narrow continental shelf of the studied region. The sightings presented here confirm the occurrence of two additional species (F. attenuata and S. frontalis) in the Bahia state, and reveal the wide diversity of cetaceans in this area. This study is an initial step to document and collaborate with the knowledge about the dolphin species that occur in the shore of Bahia.